Topical Cetirizine in Androgenetic Alopecia in Females

Androgenetic alopecia (AGA) is the most common form of alopecia in men and women. It is a hereditary, androgen-dependent, progressive thinning of scalp hair that follows a defined pattern. The disease mechanism is still relatively poorly understood, but involves a strong genetic contribution as well as some environmental input. AGA manifests as a noticeable reduction of scalp hair coverage, shorter miniaturized telogen vellus hair follicles, and significantly slower rates of hair growth. Approximately 6% to 38% of healthy women experience some degree of frontal and frontoparietal hair loss. AGA may have significant impact on quality of life in female patients. When female AGA is associated with high levels of androgens, systemic antiandrogenic therapy may be needed. However, treating it with oral antiandrogens is usually ineffective suggesting that most female AGA cases are not systemic androgen dependent and topical treatment may be more appropriate.

Currently, the only clinically validated and licensed medication approved for increasing hair density in women with AGA is 2 % minoxidil topical solution, and up to 5% minoxidil in several countries. The collective effects of minoxidil lead to increased cutaneous blood flow, prolongation of the anagen growth phase, and increase in the size of smaller hair follicles. However, it produces moderate results, and must continue to be used to have a continued benefit, and may produce adverse side effects. The use of higher concentrations of minoxidil in women is supported by results from an early study suggesting that concentrations higher than 2% could improve efficacy without increasing the rates of adverse events when applying not more than 60 mg of minoxidil per day.

Based on the hypertrichosis observed in patients treated with analogues of prostaglandin F2a (PGF2a) (i.e. latanoprost used for glaucoma), it was supposed that prostaglandins would have an important role in hair growth. Their action is variable depending on the class they belong to: prostaglandin E(PGE) and PGF2a play a generally positive role on the hair growth, while PGD2 has an inhibitory role on the hair growth. Elevated levels of prostaglandin D2 synthase (PGDS) were found at the messenger ribonucleic acid (mRNA) and protein levels in bald scalp versus haired scalp of men with AGA; as well as the enzymatic product of PGDS, (PGD2), is generally elevated in bald human scalp tissue.

Cetirizine is a safe and selective, second-generation histamine H1 receptor antagonist, widely used in daily practice. A study showed that cetirizine causes a significant reduction in both the inflammatory cell infiltrate and PGD2 production. However, these effects apparently are not related to its anti-H1 activity. A pilot study on topical cetirizine showed that cetirizine increased total hair density, terminal hair density and diameter. Also, its lower potential side effects if compared with other drugs commonly used for AGA, as minoxidil (which often cause of hypertrichosis, contact allergic dermatitis, headache and hypotension), can promote a wider use and better compliance of cetirizine in the future for the treatment of AGA. Combinations of therapies are likely to be more efficacious than single treatments.

Treatments to clinically improve scalp hair density and reduce mid-pattern thinning leading to improved scalp coverage are highly important for the affected women. On the basis of the above evidence and lacking studies that confirm the effectiveness of cetirizine in AGA treatment, the aim of this study is to evaluate the efficacy and tolerability of topical cetirizine in female patients with AGA.